Ascend Sierra Tower + Emotiva XPA-11 = Burnt Voicecoil

[highfigh]

Didn't @shadyJ clarify about playback of recorded distortion vs amplifier created distortion/clipping?

Maybe he'll show it if he did, but do you mean recorded distortion, like a guitar? I haven't seen any speakers that blew because of that and since it has been used as an effect for so long, I think we would have seen a lot more of it. The amount and type of distortion determines the sound when effect pedals are used- some cause symmetrical distortion (Ibanez Tube Screamer TS-808 style) and some cause asymmetrical distortion (Boss SD-1 Super Distortion style pedals). Since the recorded level can be extremely low in the mix, it's not the same as when the power amp connected to speakers clips the signal because it's not related to the output voltage and current.

 

[highfigh]

I listened and what jumped out at me first was the snare drum.

I think it's the third or fourth strike, possibly one of the toms- could have been loose hardware, too.

They may have done some tweaking on this version- it wasn't as audible. If you find a non-remastered version, it's very obviously distorted.

 

[jeeper]

Hi guys, so once Emotiva confirmed they have the offset protection Dave asked me to go ahead hookup the towers, and take some measurements from the speaker terminals. Here's what I just shared with him:

These were done somewhat quickly (on the advice of Dave).

 

[lovinthehd]

Maybe he'll show it if he did, but do you mean recorded distortion, like a guitar? I haven't seen any speakers that blew because of that and since it has been used as an effect for so long, I think we would have seen a lot more of it. The amount and type of distortion determines the sound when effect pedals are used- some cause symmetrical distortion (Ibanez Tube Screamer TS-808 style) and some cause asymmetrical distortion (Boss SD-1 Super Distortion style pedals). Since the recorded level can be extremely low in the mix, it's not the same as when the power amp connected to speakers clips the signal because it's not related to the output voltage and current.

That's the sort of thing I was referring to....

 

[Verdinut]

Recorded guitar distotortion, I'm distorting my text, is a second order harmonic tube amplifier distortion and is nothing compared to digital output transistor distortion. This tube amp distortion is usually not harmful to speakers unless its sound is digitally recorded and then amplified by a clipping solid state amp. The solid state output transistors are a lot more dangerous to speakers than tubes when they fully distort (clip). Another important factor is that some SS amplifiers are definitely more powerful than any tube amp.

 

[slipperybidness]

Hi guys, so once Emotiva confirmed they have the offset protection Dave asked me to go ahead hookup the towers, and take some measurements from the speaker terminals. Here's what I just shared with him:

These were done somewhat quickly (on the advice of Dave).

View attachment 52078

So, what's the conclusion of this data set?

This is measured with a simple DC voltage meter? Results are Vp, Vpp, or RMS?

 

[highfigh]

So, what's the conclusion of this data set?

This is measured with a simple DC voltage meter? Results are Vp, Vpp, or RMS?

Best done with a scope- it can handle high frequencies.

 

[jeeper]

So, what's the conclusion of this data set?

This is measured with a simple DC voltage meter? Results are Vp, Vpp, or RMS?

With my simple, household multimeter. I have no idea how the results are measured, or how to interpret. I've shared with Dave and also Emotiva support.

 

[jeeper]

Best done with a scope- it can handle high frequencies.

Probably, but I don't have one

 

[highfigh]

Probably, but I don't have one

You wouldn't want to test for distortion with speakers connected, anyway- best (and quieter) done with non-inductive load resistors.

 

[PENG]

With my simple, household multimeter. I have no idea how the results are measured, or how to interpret. I've shared with Dave and also Emotiva support.

You do not need a scope if you are just going to measured DC offset, is that's what they asked you to do?
On the multimeter you simply select it on the DC range, start with the higher range and go down once you are sure the voltage is in the mV range.

If the values you showed earlier were from the speaker terminals, at the volume positions you showed such as at -8, was the amp playing anytying/music? Or nothing?. Either way, -90 mV dc (again, if that's what you were measuring) is on the high side, though it should not cause damage to your speakers or trigger the DC offset protection.

 

[jeeper]

You do not need a scope if you are just going to measured DC offset, is that's what they asked you to do?
On the multimeter you simply select it on the DC range, start with the higher range and go down once you are sure the voltage is in the mV range.

If the values you showed earlier were from the speaker terminals, at the volume positions you showed such as at -8, was the amp playing anytying/music? Or nothing?. Either way, -90 mV dc (again, if that's what you were measuring) is on the high side, though it should not cause damage to your speakers or trigger the DC offset protection.

Yes, this is what Dave from Ascend (or IS Ascend) asked me to do once Emotiva confirmed they have DC offset protection.

The readings were from the speaker terminals, at the volumes indicated (-25, -15, -8) while music was playing.

Still waiting on Dave to respond, but here's what Emotiva had to say:

"I sent your results to my engineering team and they agree that they are completely normal numbers and not indicative of DC being a problem. Anything under 100mv should be considered perfectly fine on an amplifier, especially with content playing, as this will affect the readings. A reading of 3mv at idle is about as low as you can go, and these readings should always be taken at idle anyways. If DC offset were going to be an issue, you would see something like rail voltage on the outputs, and the amplifier would not come out of protection and keep working after such an event."

 

[TLS Guy]

Yes, this is what Dave from Ascend (or IS Ascend) asked me to do once Emotiva confirmed they have DC offset protection.

The readings were from the speaker terminals, at the volumes indicated (-25, -15, -8) while music was playing.

Still waiting on Dave to respond, but here's what Emotiva had to say:

"I sent your results to my engineering team and they agree that they are completely normal numbers and not indicative of DC being a problem. Anything under 100mv should be considered perfectly fine on an amplifier, especially with content playing, as this will affect the readings. A reading of 3mv at idle is about as low as you can go, and these readings should always be taken at idle anyways. If DC offset were going to be an issue, you would see something like rail voltage on the outputs, and the amplifier would not come out of protection and keep working after such an event."

The readings you posted were top end, but would not damage the speaker.

The problem is this fault may well be intermittent. The fact you smelt burning rubber, makes me suspicious of an episode of DC offset. Over driving will not usually result in rubber smoking. I find this whole episode disconcerting. If it was overdriving distortion would have to have been on a massive scale and obvious.

Dave is an honest fellow. Ask him how many users have had those midrange drivers get to the smoking stage.

 

[PENG]

Yes, this is what Dave from Ascend (or IS Ascend) asked me to do once Emotiva confirmed they have DC offset protection.

The readings were from the speaker terminals, at the volumes indicated (-25, -15, -8) while music was playing.

Still waiting on Dave to respond, but here's what Emotiva had to say:

"I sent your results to my engineering team and they agree that they are completely normal numbers and not indicative of DC being a problem. Anything under 100mv should be considered perfectly fine on an amplifier, especially with content playing, as this will affect the readings. A reading of 3mv at idle is about as low as you can go, and these readings should always be taken at idle anyways. If DC offset were going to be an issue, you would see something like rail voltage on the outputs, and the amplifier would not come out of protection and keep working after such an event."

Thank you for confirming what I thought would be the case. When you get it fixed, try not listen to -8 (may be -15..) again for too long and you should be fine.

 

[PENG]

If it was overdriving distortion would have to have been on a massive scale and obvious.

Could be, but as explained in that AH article I linked earlier, that would also depend on other conditions. As an example, the speakers might have been compressing if it got heated up by being driven hard for long enough time and could be self limiting the current drawn. So the distortions may not be as audibly obvious, depending on how severely it was compressing.

 

[jeeper]

Thank you for confirming what I thought would be the case. When you get it fixed, try not listen to -8 (may be -15..) again for too long and you should be fine.

<facepalm>

I usually watch movies around -11-12... And Matrix Resurrections is coming out

 

[Billy106]

<facepalm>

I usually watch movies around -11-12... And Matrix Resurrections is coming out

I wouldn't dwell on this to much. My current receiver marantz 1710(low profile) due to limitations with my credenza is only rated at ~50w and I've driven my system with music to about -10/12dbs...movies about -15dbs...ik it's all relative because my room is not large BUT it's loud without any issue. In all likelihood this occurred due to some sort of fault in the recording mix of a specific track...like was in my case yrs ago. It never happened again and fwiw...I returned my mid-range driver back to Ascend for Dave to look over and the replacement has being working flawlessly....going on 7+yrs.

 

[Pogre]

How long were they playing at volume before the mid fried? This measurement was taken using a calibrated mic at my seat, 15 feet from the front stage.

That was really, really loud. Unsafe loud, but not for more than a song or 2. Even at that I was a little nervous because the drivers were getting ready to hop out of the cabinet. This is the video I made to show Dave. My built in mic and recording skills aren't too great so you might wanna turn it down because it sounds like crap, but you can see how much my drivers (80 hz crossover) were moving at that volume.

 

[PENG]

How long were they playing at volume before the mid fried? This measurement was taken using a calibrated mic at my seat, 15 feet from the front stage.

View attachment 52124

That was really, really loud. Unsafe loud, but not for more than a song or 2. Even at that I was a little nervous because the drivers were getting ready to hop out of the cabinet. This is the video I made to show Dave. My built in mic and recording skills aren't too great so you might wanna turn it down because it sounds like crap, but you can see how much my drivers (80 hz crossover) were moving at that volume.

Wow, nice video! How hard do you think your Monolith amp (iirc) was pushing at that point?

 

[PENG]

<facepalm>

I usually watch movies around -11-12... And Matrix Resurrections is coming out

I would guess that is a safe level but if you don't mind (if that's been asked and answered before), did you use that online calculator that lots of AH members had recommended, to figure you your actual (still estimated) power need? If that is known then it will be much easier to guess the risk more accurately because then we can calculate it based on stated assumptions.